Polyester compositions containing aryl ether compounds

ABSTRACT

This invention relates to a polyester composition comprising 
     a) a polyester having repeat units from terephthalic acid and 1,4-cyclohexane dimethanol, said polyester having an I.V. of 0.5-2.0 g/dL, and 
     b) about 1-10% by weight of the total composition of an ether compound having the formula 
     wherein R and R&#39; having from about 1 to about 30 carbon atoms are univalent hydrocarbon radicals, A and A&#39; having from about 6 to about 18 carbon atoms are aromatic radicals, and --X-- is a chemical bond or divalent coupling radical.

FIELD OF THE INVENTION

This invention relates to poly(1,4-cyclohexylenedimethyleneterephthalate) compositions which have good melt flow, low cycle timesin injection molding, good weld-line strength and good melt stability.The compositions contain certain aryl ether compounds, optionally with amultifunctional epoxy-based or epoxy-derived compound and a phosphate orphosphonite compound wherein at least one of the P--O oxygens isattached to an aryl radical.

BACKGROUND OF THE INVENTION

Compositions based on poly(1,4-cyclohexylenedimethylene terephthalate),PCT, are useful as injection molding compounds for applications such aselectrical/electronic parts, automotive parts, and mechanical parts,owing to their excellent physical properties, chemical resistance, andheat resistance. The heat resistance of PCT compositions is higher thanthat which can be obtained with common thermoplastic polyesters such aspoly(ethylene terephthalate), PET, and poly(butylene terephthalate),PBT. However, for thin-walled parts, PCT is deficient in crystallizationrate and melt flow. Further, the high processing temperature needed forPCT causes the molecular weight of the polymer to degrade duringinjection molding, which in turn causes a decrease in physicalproperties. These problems prevent the wider use of PCT as a moldingmaterial.

Solutions suggested to the first problem, that of low crystallizationrate, have included the use of long chain alcohols (U.S. Pat. No.4,859,732), amide compounds (U.S. Pat. No. 4,894,404) and toluenesulfonamide (Japan Kokai H2-187451). Normal plasticizers do not providesufficient increase in the crystallization rate for good processability.Also, they are volatile and thus cause problems in mold corrosion,charring due to volatile gases, and loss of physical properties.

Regarding the problem of degradation during injection molding, it hasbeen previously disclosed to add epoxy compounds to a similarterephthalate-based polyester, PET. It has also been previouslydisclosed to add trifunctional phenol-type epoxy compounds,trifunctional isocyanuric acid-based compounds (EP-A-0273149), phenoxyresin (U.S. Pat. No. 4,837,254) and glycidyletherester compounds (JapanKokai H3-9948) to PET.

The use of certain epoxy compounds in PCT is disclosed in EP-A-273149.This application also discloses the use of a phosphate compound as acomponent of a formulation. Phosphates are not within the scope of thepresent invention. The use of other epoxy/phosphorous combinations aredisclosed in WO 9106602.

The addition of stabilizers to a blend of a PCT-type copolyester andpolycarbonate has been disclosed (Japan Kokai S62-270653).

The use of heat stabilizers to avoid color formation during heat agingof PCT copolyesters (EP-A-0328528) is also known.

Known epoxy compounds have sometimes been effective in avoiding a dropin apparent viscosity due to degradation. However, it is difficult toavoid a loss of physical properties when a drop in molecular weightoccurs. It is also difficult to obtain stable processing performance,for example, during injection molding. This is due to the polymerbranching which occurs as a result of the continuing reaction betweenthe multifunctional epoxy and the polymer melt in the injection moldingmachine. This branching causes changes in the flow characteristics ofthe polymer. Thus it is not possible to obtain sufficient melt stabilityusing only the known epoxies.

Unexpectedly, a suitable plasticizer for PCT has been discovered whichimproves crystallization rate and melt flow without lowering physicalproperties and which has a much lower level of volatile off-gas.

Further, use of specific phosphorous compounds with this plasticizergives synergistic improvements in melt stability. Use of combinations ofthe plasticizer with phosphorous compounds and with multifunctionalepoxy compounds dramatically improves the physical properties,especially after exposure of the PCT in a molten state to long residencetimes in an injection molding machine.

SUMMARY OF THE INVENTION

According to the present invention there is provided a polyester moldingcomposition comprising

a) a polyester containing repeat units derived from terephthalic acidand 1,4-cyclohexanedimethanol and having an inherent viscosity fromabout 0.5 to 2.0 g/dL,

b) about 0.1-10% by weight of the total composition of an ether compoundhaving the formula

    R--O--A--X--A'--O--R'

wherein R and R' are univalent hydrocarbon radicals, A and A' are arylradicals, and --X-- is a chemical bond or divalent coupling radical.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polymerization method used to prepare the poly(1,4-cyclohexylenedimethylene terephthalate) useful in the invention is not particularlylimited. It is typical to polycondense terephthalic acid or its alkylesters with 1,4-cyclohexanedimethanol. Polymerization conditions aregiven, for example, in U.S. Pat. No. 2,901,466.

The dicarboxylic acid component of the PCT may contain up to about 20mol %, preferably up to 10 mol %, of other conventional dicarboxylicacids such as isophthalic acid, phthalic acid,2-6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid,1,5-naphthalenedicarboxylic acid, methylphthalic acid,4,4-diphenyldicarboxylic acid, 2,2'-biphenyldicarboxylic acid,1,2-bis(4-carboxyphenoxy)ethane, succinic acid, adipic acid, subericacid, azelaic acid, sebacic acid, dodecanedicarboxylic acid,octadecanedicarboxylic acid, dimer acid, and 1,4-cyclohexanedicarboxylicacid.

The glycol component of the PCT may contain up to about 20 mol %,preferably 10 mol %, of other conventional glycols such as ethyleneglycol, propylene glycol, 1,5-pentanediol, 1,6-hexanediol,1,8-octanediol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol,2,2-bis(2'-hydroxyethoxyphenyl)propane, etc.

The 1,4-cyclohexanedimethanol used in the PCT has a cis/trans ratio inthe range of 60/40 to 10/90, preferably 50/50 to 15/85, and morepreferably 40/60 to 25/75. If the level of cis isomer is greater thanabout 60 mol %, the melting point of the polyester is reduced too muchfor use in heat resistant applications. If the level of trans isomer isgreater than about 90 mol %, the melting point increases too close tothe degradation point and molding becomes impractical.

The polyesters and copolyesters described above should have an I.V.(inherent viscosity) of about 0.5-2.0 dL/g, preferably about 0.5-1.0dL/g. At lower values, the physical properties of the polymer areadversely affected. At higher values, processability becomes difficult.

Carboxyl ends in the PCT polymer should be less than 100 eq/⁶ g ofpolymer, preferably less than 30 and more preferably less than 15. Thisvalue can be determined according to the method of H. A. Pohl,Analytical Chemistry, 26, 1614-1616 (1954).

The chemical formula of component b) of this invention, the aryl ethercompound, is generally represented by the formula

    R--O--A--X--A'--O--R'.

R and R' represent univalent hydrocarbon radicals, including aliphatic,alicyclic and aromatic radicals. Aliphatic radicals are preferred.Specific examples of aliphatic radicals are methyl, ethyl, propyl,butyl, pentyl, hexyl, octyl, decyl, dodecyl, and octadecyl. Examples ofalicyclic radicals are cyclohexyl and methylcyclohexyl. Examples ofaromatic radicals are phenyl, benzyl and naphthyl. Of these, aliphaticradicals having 5-22 carbon atoms, e.g. octyl, dodecyl, and octadecylare especially preferred.

A and A' are aromatic radicals of having about 6 to 18 carbon atoms, forexample, benzene, naphthalene, and biphenylene. More preferred aromaticradicals are p-phenylene, m-phenylene, and o-phenylene.

An even more preferred aromatic radical is p-phenylene.

--X-- represents a chemical bond alkylene group or a divalent couplingradical having about 1 to about 8 carbon atoms. Examples of divalentcoupling radicals are alkylene groups ether, thioether and sulfonyl.Preferred divalent coupling radicals are 2,2-propylidene, methylene,ethylidene, cyclohexylidene, and sulfonyl. Even more preferred divalentcoupling radicals are 2,2-propylidene and sulfonyl.

--O--A--X--A'--O-- of the above formula is commercially produced. Thesubstituted radical which eliminates hydrogen from a bisphenol isinexpensive and easy to handle. Examples of bisphenols are bisphenol-A,bisphenol-S, bisphenol-F, and bisphenol-E.

The concentration of the ether compound is 0.1-10 weight %, andpreferably 0.5-5 weight %. At levels below 0.1 weight %, theimprovements in crystallization rate and melt flow are insufficient. Atlevels above 10 weight %, physical properties are decreased.

Optionally, an organic phosphite or phosphonite wherein at least one ofthe P--O oxygens is attached to an aryl radical having about 6-30 carbonatoms may be added at a level of 0.05-2 weight % to improve meltstability. Further improvement in melt stability may be obtained by theaddition of 0.05-2 weight % of a multifunctional epoxy compound.

The phosphorous-based compound used in this invention is either aphosphite or a phosphonite or a mixture of both, wherein at least one ofthe P--O oxygens is attached to an aryl radical.

Such compounds may be represented by the formulas ##STR1## where atleast one of R₁, R₂ and R₃ is an aryl radical of 6 to 30 carbon atomssuch as phenyl, nonylphenyl, butyl phenyl, butyl methylphenyl, biphenyland octylphenyl, and any other(s) of R₁, R₂ and R₃ are H or alkyl of 1to 30 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl,octyl, decyl, dodecyl, octadecyl, cyclohexyl, isopropyl, isononyl,isooctyl and the like or ##STR2## wherein R₃, R₄ and R₅ are as definedfor R₁, R₂ and R₃ above.

Examples of these compounds are: tris-(2,4-di-t-butylphenyl)phosphite;tetrakis-(2,4-di-t--butylphenyl)-4,4'-biphenylene phosphite;bis-(2,4-di-t-butylphenyl)-pentaerythritol diphosphite;bis-(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite;2,2-methylene-bis(4,6-di-t-butylphenyl)octylphosphite;4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl)-phosphite;1,1,3-tris-(2-methyl-4-tridecylphosphite-5-t-butylphenyl)butane;tris-(mixed mono- and di-nonylphenyl)phosphite;tris-(nonylphenyl)phosphite; and4,4'-isopropylidenebis-(phenyl-dialkylphosphite).

Preferred compounds are tris-(2,4-di-t-butylphenyl)phosphite;2,2-methylenebis-(4,6-di-t-butylphenyl)-octylphosphite;bis-(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, andtetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylenephosphonite.

The epoxy compound used in this invention has two or more epoxy groupsper molecule. If there is only one epoxy group per molecule, the epoxycompound is not effective for improving melt stability, which is anobjective of this invention. A compound containing only one epoxy groupper molecule can reduce molecular weight loss from hydrolysis bydecreasing the number of carboxyl ends in the PCT. However, it ispreferable to use an epoxy compound having three or more epoxy groupsper molecule and even more preferably, three to five epoxy groups permolecule. This allows for increased melt stability to be obtained with aminimal concentration of epoxy compound.

Preferably, the epoxy compound used in the present invention is selectedfrom the group consisting of

1) aromatic hydrocarbon compounds having at least 3 epoxide groups,including monomers, oligomers or polymers of up to 10 monomer units

2) polymers derived from a diepoxide monomer of the formula ##STR3##wherein n is about 50 to 200, or 3) oligomers having 2 to about 15repeat units of diglycidyl ethers having the formula ##STR4## wherein Ris an aromatic radical of 6-15 carbon atoms.

Preferably, the compounds of 1) above have the structural formula##STR5## or are the reaction products of up to five moles of compound Iwith one mole of compound II. Commercially available compounds describedin 1) include epoxylated novolac, tris(4-glycidyloxyphenyl)methane andpolymers thereof, available from Dow Chemical Company.

The diepoxide monomer referred to in 2) above has the structural formula##STR6##

Preferably R in 3) above is ##STR7## Examples of polymers described in2) above include the polyhydroxyether of bisphenol A (commonly known asphenoxy) which is produced from 2,2'-bis(4-hydroxyphenyl) propane andepichlorohydrin. Preparation of such polymers is described in U.S. Pat.No. 3,356,646.

Commercially available compounds described in 3) include Epon oligomersof diglycidyl ether, available from Shell Chemical Company. Thesecompounds have two reactive epoxy groups and at least one secondaryhydroxyl group per molecule.

In the case of compositions based on common polyester resins such as PETand PBT, use of an epoxy compound having more than three functionalgroups results in a strong cross-linking reaction that causes anincrease in viscosity and gelation. This in turn leads to reductions inphysical and mechanical properties. This cross-linking reaction has beenused to make these resins suitable for processing by extrusion and blowmolding. PCT is different from PBT and PET, however, in that itsdecomposition rate is relatively rapid at the processing temperature.Thus, the effect of the epoxy compound is somewhat different in PCT,where it can be just effective enough to avoid the drop in physicalproperties which would accompany a decrease in molecular weight.

Examples of effective epoxy compounds are: the diglycidylethers ofaliphatic diols such as 1,6-hexanediol, neopentyl glycol, andpolyalkylene glycols; the polyglycidylethers of aliphatic polyols suchas sorbitol, sorbitane, polyglycerol, pentaerythritol, diglycerol, andglyceryl trimethylolpropane; the polyglycidylethers of alicyclicpolyols; the diglycidylester or polyglycidylester of aliphatic oraromatic multi-functional carboxylic acids such as terephthalic acid,isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, adipicacid, and sebacic acid; the diglycidyl ether or polyglycidyl ether ofmultifunctional phenols such as resorcinol,bis-(p-hydroxyphenyl)methane, 2,2-bis-(p-hydroxyphenyl)propane,tris-(p-hydroxyphenyl methane), and1,1,2,2-tetrakis-(p-hydroxyphenyl)ethane; the N-glycidyl derivatives ofamines such as N,N-diglycidyl-aniline, N,N-diglycidyltoluidine, andN,N,N',N'-tetraglycidyl-bis-p-aminophenyl)methane; triglycidylderivatives of aminophenol;triglycidyl-tris-2-hydroxyethyl)isocyanurate; ortho-cresol type epoxiesand phenol-novolac type epoxies.

The most effective compounds among the above are the polyglycidylethersof aliphatic polyols, the triglycidylether oftris-(p-hydroxyphenyl)ethane, the tetraglycidylether of1,1,2,2-tetrakis-(p-hydroxyphenyl)ethane, andtriglycidyl-tris-(2-hydroxyphenyl)isocyanurate. The epoxy compound canbe added in a monomeric form, or in the form of a condensedoligomer/polymer, or as a mixture. The polymerization degree ispreferably 1-20, more preferably 1-10. Mixtures of different epoxycompounds are also possible. The methods used to make the epoxycompounds are not restricted. Typical methods are disclosed in thereferences cited above, as well as in Encyclopedia of Polymer Scienceand Engineering, published by John Wiley and Sons.

The level of epoxy compound used in this invention should be in therange of 0.05-5 weight %, preferably 0.1-3 weight %, based on 100 weight% of the total PCT formulation. If a level of less than 0.05 weight % isused, the improvement in stability is insufficient. If more than 5weight % is used, the physical properties of the PCT are decreased.Among the epoxy compounds, the glycidylester type and the N-substitutedglycidyl derivatives have higher reactivities compared to theglycidylether types; thus, they can be used at lower levels. For optimumprocessability, melt. stability, and thermal stability during drying,the amount of epoxy compound should be adjusted to about 30equivalents/10⁶ grams of polymer, preferably 20 equivalents/10⁶ grams ofpolymer.

The combination of a multifunctional epoxy compound with the specifiedphosphorous compounds has a synergistic effect on the melt stability ofPCT and avoids loss of mechanical properties resulting from longresidence times in the melt, as may occur in an injection moldingmachine. It is believed that the combination of additives suppresses thechain branching that occurs when the multifunctional epoxy is usedalone, and this is responsible for the improved performance.

It is possible to use the epoxy compounds disclosed above withhydrolytic stabilizers such as oxazolines, carboxyimides and azylidines.

It is also possible to use reinforcing materials in this invention.These can be fiber, bead or flake types, i.e. glass fiber, glass beads,glass flake, carbon fiber, ceramic fiber, asbestos, wollastonite, talc,clay, mica, celicite, zeolite, bentonite, dolomite, kaolin, silicates,powdered feldspar, potassium titanate, calcium carbonate, magnesiumcarbonate, barium sulfate, calcium oxide, aluminum oxide, titaniumoxide, aluminum silicate, silicon dioxide, plaster, novacurite, dosoniteand white earth. These can be used individually or in mixtures of two ormore types. Preferred are glass fiber, glass beads, wollastonite, mica,clay, and talc. Reinforcing materials may be used at levels of 5-60 wt.%.

The composition of this invention can also include one or more of thefollowing: antioxidants, ultraviolet stabilizers, heat stabilizers,lubricants, mold release agents, dyes, coloring agents includingpigments, impact modifiers, flame retardants, and the like. Theseadditives should be present at levels that do not affect the mainpurpose of the invention.

It is desirable to include a nucleating agent as a component of thisinvention to further improve the processability. Preferred nucleatingagents are metal salts of aliphatic carboxylic acids such as sodiumstearate and barium stearate; sodium montanate; the sodium salt ofbenzoic acid and its derivatives; the sodium salt of salicylic acid; thesodium salts of substituted phenols such as nitrophenol, salicylanilineand salicylaldehyde; the sodium salt of copolymers of ethylene andacrylic acid or methacrylic acid; and inorganic powders such as talc andclay.

It is also possible to add small amounts of other polymers such aspolyethylene, acrylics, fluorocarbons, polyamides, poly(ethyleneterephthalate), poly(butylene terephthalate), poly(phenylene sulfide),polyetheretherketone, liquid crystal polyester, polyacetal,polycarbonates, polysulfones, polyphenylene oxides, thermoset resins(for example phenol, melamine, polyester, silicone, or epoxy resins),ethylene/vinyl acetate copolymers, polyester elastomers,ethylene/propylene terpolymers, and the like.

Compounding of the aryl ether compound, the multifunctional epoxycompound and the organic phosphorous compound into PCT can beaccomplished by any convenient method, though extrusion is typicallyused. The compounding temperature.must be above the melting point of thePCT resin. Parts from the compositions of this invention can be formedby known methods such as injection molding and extrusion. Such partshave excellent mechanical properties and chemical resistance which makethem suitable for use in applications such as electrical/electronics,automotive, mechanical, and other intricate moldings.

As used herein, the inherent viscosity (I.V.) of the polyester ismeasured at 25° C. using 0.5 g of polymer per 100 mL of a solventconsisting of 60% by weight phenol and 40% by weight tetrachloroethane.The intrinsic viscosity of the polyphenylene ether is measured at 25° C.in chloroform.

The invention can be further illustrated by the following examples ofpreferred embodiments thereof, although it will be understood that theseexamples are included merely for purposes of illustration and are notintended to limit the scope of the invention unless otherwisespecifically indicated. All percentages are by weight, unless otherwisespecified.

EXAMPLES 1-9

Examples 1-8 are examples of the invention. Example 9 is a comparativeexample.

In the following examples, all compositions are given in weight %. Thefollowing materials were used:

PCT 0.81 I.V.; cis/trans ratio of CHDM 30/70; carboxyl ends=12equivalents/10⁶ g polymer

35 weight % chopped strand glass fiber (10 micron diameter, 3 mm length)

0.5 weight % talc

Ether Compound ##STR8## Epoxy Tetraglycidylether of1,1,2,2-tetrakis-(p-hydroxyphenyl)ethane (B-1)Triglycidyl-tris-(2-hydroxyethyl)-isocyanurate (B-2) Triglycidylether oftris-(p-hydroxyphenyl)methane (B-3) Pentaerythritol tetraglycidylether(B-4)

Phosphorous CompoundBis-(2,4-di-t--butyl-4-methylphenyl)-pentaerythritol diphosphite (C-1)

2,2-Methylene-bis-(4,6-di-t-butylphenyl )octylphosphite (C-2 )

Tetrakis-(2,4-di-t-butylphenyl)-4,4'biphenylphosphonite (C-3)

Crystallization rate was measured by determining the crystallizationtemperature on heating (Tch) and on cooling (Tcc) using a Perkin-ElmerDifferential Scanning Calorimeter. It is well known in the art thathigher Tch's or lower Tcc's indicate faster crystallization rates. Thusthe value ΔT=Tch-Tcc can be used as a measure of crystallization rate.

The set temperature of the compounding extruder was 300° C. Aftercompounding, the polyester composite was dried at 130° C. for fourhours. Sample bars (ASTM type I dumbbell, 1/8" thick, with and withoutweld) were molded on a screw-in-line type injection molding machinehaving a 75 MT clamping force. Mold temperature was 120° C. and thecycle time was 30 sec. Also, to determine the effect of residence timein the molding machine, samples without a weld-line were molded using acycle time of 120 sec. Tensile tests were done according to ASTM D638.

Processability was evaluated by determining the minimum cycle time tomold a small box, 100 mm×50 mm×30 mm×2 mm thick.

Results are shown in Table 1, where it can be seen that, surprisingly,improved weld-line strengths and cycle times are obtained with thecompositions of this invention (those containing the ether compounds).Further, the addition of a multifunctional epoxy compound and a specificphosphorous compound improves the mechanical properties and the meltstability. Compositions of this invention have an excellent combinationof heat resistance, melt flow, cycle time, weld-line strength, and meltstability making them useful for applications in the areas ofelectrical/electronics, automotive, mechanical and structural parts.

                                      TABLE 1                                     __________________________________________________________________________                Multi-           Cycle Time Cycle Time                                        functional       (30 sec.)  (120 sec.)                                                                             Min.                         Ether       Epoxy  Phosphorus                                                                              Tensile Strength                                                                         Tensile Strength                                                                       Cycle                        Compound    Compound                                                                             Compound                                                                             ΔT                                                                         [kg/cm.sup.2 ]                                                                           [kg/cm.sup.2 ]                                                                         Time                         Type    Wt. %                                                                             Type                                                                             Wt. %                                                                             Type                                                                             Wt. %                                                                             (°C.)                                                                     W/Weld                                                                             W/O Weld                                                                            W/O Weld (sec.)                       __________________________________________________________________________    Act.                                                                          Example                                                                       1    A-1                                                                              3.5 -- --  -- --  123                                                                              1110 520    810     15                           2    A-1                                                                              3.5 B-1                                                                              0.5 -- --  117                                                                              1290 570    920     28                           3    A-1                                                                              3.5 -- --  C-1                                                                              0.25                                                                              123                                                                              1210 540    900     14                           4    A-1                                                                              3.5 B-1                                                                              0.5 C-1                                                                              0.25                                                                              123                                                                              1310 620   1110     13                           5    A-2                                                                              3.5 B-2                                                                              0.5 C-2                                                                              0.25                                                                              122                                                                              1310 610   1140     16                           6    A-3                                                                              3.5 B-3                                                                              0.5 C-3                                                                              0.25                                                                              123                                                                              1330 620   1140     13                           7    A-4                                                                              3.5 B-4                                                                              0.5 C-1                                                                              0.25                                                                              126                                                                              1340 620   1120     15                           8    A-4                                                                              3.5 B-3                                                                              0.5 C-1                                                                              0.25                                                                              124                                                                              1310 610   1150     14                           Com. -- --  B-1                                                                              0.5 C-1                                                                              0.25                                                                              113                                                                              Impossible to Mold                                                                       1100     60                           Example                                                                       __________________________________________________________________________     Act. Ex. = Actual Example                                                     Com. Ex. = Comparison Example?                                                Ether Compound                                                                ##STR9##                                                                      ##STR10##                                                                     Epoxy Compound                                                                B1: tetraglycidylether of 1,1,2,2tetrakis-(p-hydroxyphenyl)ethanol            B2: triglycidyl tris (2hydroxyethyl)isocyanurate                              B3: triglycidylether of tris(p-hydroxyphenyl)methane                          B4: pentaerythritol tetraglycidylether                                        Phosphorus Compound                                                           C1: bis (2,4di-t-butyl-4-methylphenyl)pentaerythritoldiphosphite              C2: 2,2methylene-bis(4,6-di-t-butylphenyl)octylphosphite                      C3: tetrakis (2,4di-t-butylphenyl)-4,4'-biphenylphosphonite              

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention. Moreover, all patents, patent applications (published orunpublished, foreign or domestic), literature references or otherpublications noted above are incorporated herein by reference for anydisclosure pertinent to the practice of this invention.

We claim:
 1. An injection moldable polyester composition comprisinga) apolyester having repeat units derived from terephthalic acid and1,4-cyclohexane dimethanol, said polyester having an I.V. of 0.5-2.0g/dL, as measured at 25° C. using 0.5 g of polymer per 100 mL of asolvent consisting of 60% by weight phenol and 40% by weighttetrachloroethane, and b) about 1-10% by weight of the total compositionof an ether compound having the formula

    R--O--A--X--A'--O--R'

wherein R and R'having from about 1 to about 30 carbon atoms areunivalent hydrocarbon radicals, A and A' having from about 6 to about 18carbon atoms are aromatic radicals selected from the group consisting ofbenzene, naphthalene and biphenylene, and --X-- is a chemical bond,alkylene group or divalent coupling radical.
 2. The polyestercomposition of claim 1 wherein said polyester ispoly(1,4-cyclohexylenedimethylene terephthalate).
 3. The polyestercomposition of claim 2 wherein said 1,4-cyclohexanedimethanol has acis/trans ratio in the range of 60/40 to 10/90.
 4. The polyestercomposition of claim 1 wherein said polyester contains carboxyl endswhich are less than about 100 eq/10⁶ g of polymer.
 5. The polyestercomposition of claim 1 wherein said univalent hydrocarbon radicalsinclude aliphatic, alicyclic or aromatic radicals.
 6. The polyestercomposition of claim 5 wherein said univalent hydrocarbon radical isaliphatic.
 7. The polyester composition of claim 6 wherein saidaliphatic radical has from about 5 to about 22 carbon atoms.
 8. Thepolyester composition of claim 7 wherein said aliphatic radicals areselected from the group consisting of octyl, dodecyl, and octadecyl. 9.The polyester composition of claim 1 wherein either or both of said Aand A' are selected from the group consisting of benzene, naphthalene,biphenylene, p-phenylene, m-phenylene, and o-phenylene.
 10. Thepolyester composition of claim 9 wherein either or both of said A or A'are p-phenylene.
 11. The polyester composition of claim 1 wherein said--X-- divalent coupling radical is selected from the group consisting ofalkylene group, ether, thioether, sulfonyl, 2,2-propylidene, methylene,ethylidene, cyclohexylidene and sulfonyl.
 12. The polyester compositionof claim 11 wherein said divalent coupling radical is selected from thegroup consisting of 2,2-propylidene, methylene, ethylidene,cyclohexylidene, and sulfonyl.
 13. The polyester composition of claim 12wherein said divalent coupling radical is selected from the groupconsisting of 2,2-propylidene and sulfonyl.
 14. The polyestercomposition of claim 1 further comprising a phosphite, a phosphonitecompound, or a mixture thereof.
 15. The polyester composition of claim 1further comprising an organic phosphite or phosphonite compound whereinat least one of the P--O oxygen is attached to an aryl radical.
 16. Thepolyester composition of claim 15 wherein said organic phosphitecompound is represented by the formula: ##STR11## where at least one ofR₁, R₂ and R₃ is an aryl radical of 6 to 30 carbon atoms and any otherof R₁, R₂ and R₃ are H or alkyl of 1 to 30 carbon atoms.
 17. Thepolyester composition of claim 15 wherein said organic phosphonitecompounds is represented by the formula ##STR12## where at least one ofR₃, R₄ and R₅ is an aryl radical of 6 to 30 carbon atoms and any otherof R₃, R₄ and R₅ are H or alkyl of 1 to 30 carbon atoms.
 18. Thepolyester composition of claim 16 wherein said organic phosphitecompound is selected from the group consisting oftris-(2,4-di-t-butylphenyl)phosphite;2,2-methylenebis--(4,6-bi-t-butylphenyl)octylphosphite; andbis-(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite.
 19. Thepolyester composition of claim 17 wherein said organic phosphonitecompound is tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylenephosphonite.20. The polyester composition of claim 15 wherein the total level foreither or both of said phosphite or phosphonite compounds is in therange of about 0.5-2.0 weight %.
 21. The polyester composition of claim1 further comprising a multifunctional epoxy compound.
 22. The polyestercomposition of claim 21 wherein said epoxy compound contains at leasttwo or more epoxy groups per molecule.
 23. The polyester composition ofclaim 22 wherein said epoxy compound contains three or more epoxy groupsper molecule.
 24. The polyester composition of claim 23 wherein saidepoxy compound contains three to five epoxy groups per molecule.
 25. Thepolyester composition of claim 22 wherein said epoxy compound isselected from the group consisting of tetraglycidylether of1,1,2,2-tetrakis-(p-hydroxy-phenyl)ethane, andtriglycidyl-tris-(2-hydroxyphenyl)-isocyanurate.
 26. The polyestercomposition of claim 22 wherein said epoxy compound is selected from thegroup consisting of N-glycidyl derivatives of amines anddiglycidylesters or polyglycidyesters of aliphatic or aromatic multifunctional carboxylic acids.
 27. The polyester composition of claim 21wherein said epoxy compound is present in the amount of 0.1-0.3 weight %based on the total composition.